This happens to me sometimes. I suspect it is a mix of tea tannins and leaf wax, but this is just a guess. I find this film tends to form when the a concentrated brew of tea gets cold. Maybe this is what you are referring to?

I find that brewing with a somewhat lower temperature and/or smaller quantity of leaves tend to stop the formation of this film. As well, brews of higher quality teas teand to not form this film.

bit late reply ;o), but anyway..
I used to work in the tearoom for few years, and our experience was, that black tea usually makes after some time kind of oily film. Green tea not so often and needs to get more cold than black tea.
And what you're talking about are scented teas - and God knows, what they put in. But the sure thing is, that scented teas do this kind of thing almost everytime. 1-because they're made from black tea, 2-because, they have some added ingredients.
But as I've said before, even if there is nothing added, lot of times even pure black leaf tea will make this kind of film. More cold it gets, stronger the film will be. Try to make a brew and leave it over night.. ;o)

If you want really good bang for your buck when it comes to filtering your water, I'd highly recommend the AQ-4000 by Aquasana. That's what I use when I'm at college and it has definitely been well worth it. It's 92 bucks but the filters last 6 months or up to 500 gallons, and it's way cheaper in the longrun than having to go buy bottled water all the time.

I don't know what your area is like but if you can get access to spring water that's also a pretty good route to go. We have a spring a few minutes from the house here so that's what I use when I'm here at home. Hope that helps!

I know exactly what you mean. When I was at college, every time I brewed a cup I got that oily film, yet, when I was at home brewing the same tea I would not get the film. For me, the issue was the water.

In my state, everyone has problems with "hard water," or water in which calcium and magnesium ions have dissolved. It's not a bad thing health wise, but it is obnoxious life wise. The water doesn't taste very good and everything is harder to wash, especially if the water isn't softened. Even with softened water, though, plenty of calcium and magnesium ions get through.

Here's the deal with hard water and tea/coffee making, though. When you heat hard water, the ions actually like it more and have a great time bouncing around in the aqueous suspension, knocking into other ions and forming small complexes. Once the water begins to cool, though, these complexes rapidly precipitate out (form small solids). This is what builds up on things used to heat water (tea kettles) and is often referred to as "scale." If the water is even fairly hard, though, you can also see the precipitates in the cooled water, often appearing as a white-looking "dust" or "dirt" in the bottom of a glass and as a thin, almost imperceptible film around the meniscus (surface).

When you brew black tea, tannins bind to this film and make it more easily seen--the oily film. It's still there in greens and whites, but a little more invisible. It won't hurt you at all, but it is disgusting.

Brita filters or other activated charcoal filters aren't exactly the most effective tool for dealing with hard water. Activated charcoal is primarily used to minimize chlorine ions and organic chemicals, which have different charges and properties than magnesium and calcium. This is why most household filters (including Brita) actually consist of two different filtration products. The problem is that the stuff that grabs calcium and magnesium has a shorter life, both because of the nature of the product and the fact that the water is GLUTTED with these ions. The filter turnover would make this type of product unfeasable in the long run.

You may want to look into getting a "reverse osmosis" system. The product mentioned in the previous post sounds a bit like one, but I didn't check that. Such a system will often have an activated charcoal filter, but will also have an additional semipermeable membrane. Basically, water is forced through the membrane, which acts as a very fine filter that only allows H2O molecules through. It's very, very pure stuff.

At my school, the water was not softened in the student houses, so we did the best we could with Brita. My parent's, however, invested in an RO system when I was 7. Their system was this giant thing that took up most of the space below the kitchen sink, and it had a separate spigot on the basin. However, this thing also allowed them to run a pipe from the RO system to the fridge, which had an automatic water and ice dispenser. That way, all the water making our ice and the stuff we primarily drank was clean and very convenient. I think it probably cost them $300-$400 initially, and the filters were probably $50 or so. I do know, however, that they only had to replace the membrane once every five years. I think they had once figured out that it would cost them less than a nickel a gallon in the long run.

Oh yeah, you know that hard water scale that builds up in the teapot? It's the worst thing in the world to scrub out. But you don't need to scrub.

Just fill the kettle/pot/whatever about a quarter-full with plain white vinegar, let it set a bit, then swirl the vinegar around to get the sides of the pot. The scale will dissolve, and anything that doesn't can be much easily removed with vinegar and a paper towel.

Thoroughly rinse out the vinegar with tap water, then dry with a paper towel. I do this anywhere between once a month and once every 2 weeks, depending on the amount of buildup.

Since I drilled a new and deeper well, it seems that the scale is 10X worse than before. Actually, the water has a nice "sweet" taste to it....but I hate to think what the inside of my hot water pipes look like.

We have a well and had some trouble with our water softening system and iron removal system. I have an oil slick on my tea too, or whatever it is we are brewing, like coffee. Anyway, it is called iron bacteria.

"Although iron bacteria are not harmful, they can develop quite rapidly in a well system forming slimy masses that adhere to the inside surfaces of the plumbing system. Because of their remarkable growth rate, in many cases, they impart unpleasant tastes, odors and color to the water." From Hague Water Conditioning Systems, Groveport, Ohio.

If you have a well (I am guilty of not reading all the posts because I was so excited to help you out), I suggest you contact your County Board of Health and ask for a pamphlet on "shocking" your well. This should at least be a good first step.

I have a scummy film on my tea despite using a 3-stage PUR tap filter, but it's due to heavy dissolved minerals in the public water supply. My 2-month old filter holder leaks, causing what I think is a short circuiting of the filter and resulting in a palpable mineral deposit on the outlet of the filter module. This prompted me to fire off a letter to their customer service group. I was sent a coupon for a replacement tap-mount unit.

My city has very hard water with a high mineral content, a legacy of geology and overuse of ammonium sulfate, promoting acidification of percolated irrigation water. I am going through a water purification cartridge a month. It may be that the ion exchange resin is whimpy and it's being saturated within a few weeks of installation, although the leak is complicating matters. I'll be picking up a new tap mount filter today or tomorrow, thankfully.

Second and third infusions are nearly dead in flavor and aroma because of the buildup of mineral scum film. The film consists of tea oils chelating dissolved minerals in the water, forming insoluble, low density whitish film on tea leaves. To the best of my knowledge, there is no iron-sulfur problem in this water supply, so its not caused by filamentous bacterial growth.

When we moved to Montana, our well had so much iron that it stained the sinks and toilets. The water heater had been replaced once already before we bought the house. We decided to spend the money and add a filtration system.

Best money we've spent. I still use the Brita for drinking water and making tea but now I'm assured I won't have my house plumbing ruined by the excessive minerals.

Oh, and as an FYI, I've seen oily residue with certain black teas usually coming from one particular famous bagged tea maker. I don't know why it is -- possibly where they get their tea...

I agree with the above posters, it's probably to do with hard water. I almost never get this film on my tea but when I do it's usually on very strong black tea, CTC Assams and the like.

A couple of friends went to university some 40 km's from where I live in a city with very hard water(where I live the water has a pH of 5 or 6, theirs was 8 or above) and whenever I had tea at their house I would notice a thick layer of...something floating on top :S All their cups looked really bad on the inside, too.

My tap water where I am (Canada, ottawa) is kind of cloudy, greyish "dirty" looking.I took my tap filter off and some small leaves and rocks came out (tiny pebble size).I know they are still doing construction for water for the houses beside me, so surely from them redoing the water mains here...

If you are drinking flavored teas, I bet it is from the flavorings themselves.I only have a similar thing happen w flavored teas and esp if they are iced and left in the fridge.

Also,another thing is with flavored teas you do not really know what the "natural flavor" is from...is it flavor oil? fruit juice and combination of the two?most places will not tell you what the "natural flavor" is also....that is a "company secret" usually and they do not have to disclose that.

I do know the black tea I buy the lychee flavor is from the peels only as it is called lychee scented tea. smells more like lychee than tastes it.